1. Field of the Invention
The present invention relates to an anti-chattering contact structure for a blade spring contact point, particularly for a collision detecting apparatus, which mechanically operates by inertia to start a passenger protective system such as an air bag apparatus.
2. Related Arts
A mechanical collision detecting apparatus for starting a passenger protective system such as an air bag apparatus conventionally has a structure shown in FIG. 4, which is disclosed in JP-A-8-264088. In the collision detecting apparatus 20, a weight 14 is eccentrically and rotatably supported by a shaft 15. A rotor 11 formed with a first cam 11a and a second cam 11b is fixed to the weight 14. The first and second cams 11a, 11b are respectively biased by front end portions of blade springs 12, 13 with bias forces in B direction. The blade springs 12, 13 prevent the weight 14 from rotating in an A direction by low level deceleration caused when a vehicle moves. When the vehicle collides with an object to produce high level deceleration, the weight 14 rotates together with the rotor 11 in the A direction against the bias forces of the blade springs 12, 13. Due to the rotation of the rotor 11, the blade springs 12, 13 are displaced, so that contact points 12a, 13a respectively provided on the blade springs 12, 13 contact each other to output a detection signal As a result, the collision of the vehicle is detected.
However, this kind of collision detecting apparatus 20 is usually installed in a front fender disposed on a left or right side of the vehicle. Therefore, the deceleration caused by the collision to be applied to the collision detecting apparatus 20 is liable to have a large magnitude. Upon receiving the deceleration with the high magnitude, the blade spring 13 is liable to vibrate when contacting (receiving) the blade spring 12, resulting in chattering of the detection signal outputted from the collision detecting apparatus. Therefore, it is difficult for the collision detecting apparatus 20 to output a stable detection signal.
If a minimum load (contact load) necessary for holding an ON-state (contacting state) of the contact points 12a, 13a is increased, the chattering of the detection signal can be mitigated. To increase the contact load, it is effective to thicken the blade spring 12 and to increase an initial deflection amount of the blade spring 12. However, as the blade spring 12 is thickened, it becomes difficult for the blade spring 12 to be elastically deflected, resulting in decrease in the initial deflection amount of the blade spring. Therefore, this method cannot sufficiently prevent the chattering of the detection signal.